WO2006025465A1

WO2006025465A1 - Flat perforated pipe and heat exchanger

Info

Publication number: WO2006025465A1
Application number: PCT/JP2005/015940
Authority: WO
Inventors: Takahide Maezawa; Yasuhiro Kawatsu
Original assignee: Gac Corporation
Priority date: 2004-08-31
Filing date: 2005-08-31
Publication date: 2006-03-09
Also published as: CN100516755C; JP4664918B2; CN101010552A; US20080087408A1; EP1795848A1; JPWO2006025465A1

Abstract

A flat perforated pipe, comprising a flat outer pipe and a plurality of partition walls partitioning the inside of the outer pipe into a plurality of flow passages. The partition walls of the flat perforated pipe are formed in a cross sectional shape with a thickness of (ti) in a chevron form comprising two of a side with a length of (a), and disposed so that face-to-face distances between the partition walls on the inner surface of the outer pipe are (Li). The thickness (to) of the outer pipe meets the following requirement. By properly selecting a pressure to expand the flat perforated pipe, the outer surface of the pipe can be prevented from being deformed in a waveform shape or an irregular shape.

Description

Flat multi-hole tube and heat exchanger

Technical field

[0001] The present invention relates to a structure of a flat multi-hole tube used for heat exchange.

Background art

[0002] As heat exchange ^^ used in refrigeration equipment, radiators, etc., plate fins arranged in parallel at regular intervals and a plurality of tubes (tubes) arranged so as to penetrate these fins There is known a plate fin type heat exchanger having One method for producing this plate fin type heat exchange is to join the pipe and the fin by expanding or expanding the pipe after the pipe is assembled so as to penetrate the fin. To expand these tubes, insert a rigid rod or expander inside the tubes and push the tubes inwardly. By expanding the tube, the tube and the fin come into contact.

[0003] In heat exchangers, it is known to use a flat multi-hole tube having a plurality of partition walls inside and divided into a plurality of parallel flow paths by using them.

[0004] Japanese Patent Application Laid-Open No. 62-19691 discloses a conduit having an elliptical or rectangular cross section. This conduit is pressed against the cooling fins by expansion of the surface of the conduit between each pair of joints. As the conduit expands, the joint flattens the initial chevron shape and prevents the conduit wall from contracting to its original position.

Disclosure of the invention

One embodiment of the present invention is a flat multi-hole tube having a flat outer tube and a plurality of partition walls that divide the inside of the outer tube into a plurality of flow paths. Each partition wall has a thickness ti, has a cross-sectional shape bent into two chevrons with one side length a, and is arranged so that the distance between the partition wall surfaces on the inner surface of the outer tube is a distance Li. The thickness to of the outer tube satisfies the condition (1) shown in the following formula.

[0006] [Equation 1]

Li'ti a ^ -ti There is a method of expanding by inserting a tube expander into a flow path of a flat multi-hole tube. In addition, it has been studied to extend the partition wall by injecting fluid into a flat multi-hole tube (tube) and increasing the internal pressure. Whether this is a method for increasing the internal pressure of the tube (hereinafter, sometimes referred to as “pressure expansion”) or expansion by a tube expander, the outer tube between the partition walls (hereinafter referred to as the expansion tube) It is not preferable that the outer wall) expands and the outer surface of the tube is deformed into corrugations or irregularities. The contact area between the pipe outer surface and the fin is reduced, and the heat transfer performance is reduced. However, if the expansion is stopped before the partition wall extends to the desired size, the desired performance cannot be obtained.

[0008] When considering the phenomenon that a partition bent into a Yamagata ("K" shape in Japanese hiragana) extends, initially, the two sides of the Yamagata are formed by the tensile force acting on both ends of the partition. Deforms so that the angle between them opens (becomes larger). When the angle formed by the two sides reaches a certain size, the deformation that increases the angle (the deformation that changes the inclination of the partition wall) is almost eliminated, and the inclination of the partition wall is not changed (the state of stretching). Then, due to the tensile force acting on both ends of the partition wall, the thickness of the partition wall is reduced (called tensile deformation). The stress that changes the slope of the bulkhead is different from the stress that causes the wall thickness to be reduced by tensile deformation of the bulkhead, and the stress that changes the slope of the bulkhead is smaller.

[0009] In a flat multi-hole tube having an outer tube with a thickness that satisfies the above condition (1), the outer wall that is a portion between the partition walls of the outer tube is not deformed in a pressure range that changes the inclination of the partition wall. . Therefore, a flat multi-hole tube that satisfies the above condition (1) can prevent deformation of the outer wall until the partition wall is fully extended. Therefore, this flat multi-hole tube can be expanded in a state where the outer surface of the tube is prevented from being deformed into corrugations or irregularities due to the internal pressure within the range in which the inclination of the partition wall is deformed.

[0010] The deformation amount of the partition wall inclination varies depending on the tolerance of the flat multi-hole tube and the fluctuation of the applied pressure. For this reason, it is preferable to expand the tube with the maximum pressure (internal pressure) within the range where the inclination of the partition wall is deformed or higher. By expanding the tube at such a pressure, it is possible to expand the tube to a state where the inclination of the partition wall is substantially extended. Therefore, when expanding the tube, the flat multi-hole tube can be expanded to a desired state without performing fine pressure control. Conversely, if the outer tube thickness to falls outside the range of condition (1) and the outer tube thickness to decreases, deformation of the outer tube may begin before the bulkhead extends. Therefore, it is difficult to control the pressure when expanding the pipe. [0011] Another embodiment of the present invention includes a plurality of flat multi-hole tubes satisfying the above condition (1), and a plurality of fins attached in a state in which the plurality of flat multi-hole tubes penetrate. And a heat exchanger. As described above, a flat multi-hole tube satisfying the condition (1) can be applied to a partition wall while suppressing deformation of the outer wall, regardless of whether it is a pressure expansion using a fluid or a tube expansion using a tube expander. Can be stretched. For this reason, after the pipe expansion, the contact efficiency between the plurality of flat multi-hole pipes and the plate fins attached in a state in which they are penetrated can be increased. Therefore, the heat exchange efficiency in the heat exchanger can be improved. In particular, a pressurized expanded tube using fluid is suitable for expanding almost all of the fine flow paths of a flat multi-hole tube that does not require insertion of a tube expander.

Another embodiment of the present invention is a flat multi-hole tube in which, in addition to the above condition (1), the thickness of the outer tube further satisfies the following condition (2).

[0013] [Equation 2]

[0014] Increasing the thickness of the outer tube of a flat multi-hole tube having a plurality of partition walls up to the thickness of the outer tube required for a flat tube not having a partition wall is a reduction in product size and weight. It is not economical from the viewpoint of traps. One of the merits of using a flat multi-hole tube is that the strength of the flat tube can be secured by installing a partition wall inside, so that the outer wall or the outer tube can be made thinner.

[0015] Another embodiment of the present invention is a flat multi-hole tube in which, in addition to the above condition (1), the thickness of the outer tube further satisfies the following condition (3).

[0016] [Equation 3]

A pressure higher than the pressure at the time of expanding does not become a normal pressure in the flat multi-hole tube. If such pressure is constantly applied, the flat multi-hole tube may be further deformed. No counting is done. Therefore, the pressure when expanding the tube becomes the upper limit or higher of the pressure resistance condition in normal use. Furthermore, the pressure at the time of expanding the tube is such that the partition wall is in a stretched state, and is not set to a pressure at which tensile deformation accompanied by thinning is started. For this reason, it is economical to set the thickness of the outer tube so that the outer wall is also deformed at the pressure at which tensile deformation accompanied by thinning occurs, and the thinner the outer tube, the better the heat transfer coefficient.

[0018] Further, in the case of a flat multi-hole tube satisfying the condition (3), when an excessive internal pressure is applied such that the partition wall is tensilely deformed when expanding the pressure, the outer wall expands and the outer surface of the tube is deformed. there's a possibility that. Therefore, the condition of the outer surface of the pipe can be an element for checking the pressure condition when the pipe is expanded.

Brief Description of Drawings

[0019] FIG. 1 shows an outline of heat exchange.

[Fig. 2] Shows the state where the flat multi-hole tube and fins of the heat exchanger shown in Fig. 1 are joined.

[FIG. 3] FIG. 3 (a) shows the state of the flat multi-hole tube before expansion in a cross section in the major axis direction, and FIG.

[Fig. 4] Fig. 4 (a) shows the state of the flat multi-hole tube after expansion in a cross-section in the long axis direction, and Fig. 4 (b) shows the end of the flat multi-hole tube in a cross-section in the short axis direction. Figure 4 (c) shows the other part of the flat multi-hole tube in a cross section in the minor axis direction.

[FIG. 5] FIG. 5 (a) shows a state in which the partition wall undergoes angular deformation, and FIG. 5 (b) shows a state in which the partition wall undergoes tensile deformation.

FIG. 6 shows an enlarged cross section of a flat multi-hole tube.

[FIG. 7] FIG. 7 shows changes in the inner diameter of the flat multi-hole tube when the internal pressure is increased.

[Fig. 8] Fig. 8 shows how the amount of expansion of flat multi-hole tubes varies due to tolerances.

FIG. 9 shows an example of the upper and lower limits of the thickness of the outer tube of a flat multi-hole tube.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 schematically shows a heat exchanger using a flat multi-hole tube. FIG. 2 is an enlarged perspective view showing a state where the flat multi-hole tube is expanded. The heat exchanger 1 is a plate fin type heat exchanger, and a plurality of plate-like fins arranged in parallel at regular intervals. 2 and a plurality of flat multi-hole tubes 3 which are joined in parallel to the fins 2 and arranged in parallel. These flat multi-hole tubes 3 are tubes in which the inside of the flat outer tube 21 is divided into a plurality of parallel flow paths 14 by a plurality of partition walls 15. The ends 4 on both sides of the flat multi-hole tube 3 are connected to joint holes 19 formed in the side walls 9 of the headers 6 and 7 located on the left and right of the heat exchange. The heat medium (internal fluid) introduced from the supply port 11 of the header 6 is guided to the output port 12 of the header 7 through the flow path 14 of the flat multi-hole tube 3. When an external fluid such as air is passed through the heat exchanger 1, the external fluid B comes into contact with the flat multi-hole tube 3 and the fin 2, and heat is exchanged between the heat medium and the external fluid. The fluid is cooled or heated.

FIG. 3 (a) shows a state before the flat multi-hole tube 3 is expanded. When manufacturing the heat exchanger 1, the flat multi-hole tube 3 is inserted into the burring hole 18 provided in advance in the fin 2, and the fin 2 and the flat multi-hole tube 3 are temporarily assembled.

FIG. 3 (b) shows an enlarged cross section of the flat multi-hole tube 3. The outer tube 21 of the flat multi-hole tube 3 includes an outer wall 21w facing up and down. The flat multi-hole tube 3 is a flat tube formed such that the outer wall 21 w constituting the upper wall or the top wall of the outer tube 21 and the outer wall 21 w constituting the lower wall or the bottom wall are substantially parallel to each other. It is a tube. This flat multi-hole tube 3 is provided with a plurality of partition walls 15 connected to the upper and lower outer walls 21w inside thereof, each of which has a mountain shape and is bent in the major axis direction X of the cross-section of the flat multi-hole tube 3. Yes. By these partition walls 15, the inside of the flat multi-hole tube 3 is divided to form a plurality of parallel flow paths 14.

The end 4 of the flat multi-hole tube 3 temporarily assembled so as to penetrate the fin 2 is inserted into a joint hole 19 provided in the headers 6 and 7. These ends 4 are joined to headers 6 and 7 by brazing or other suitable method. The parallel flow paths 14 of each flat multi-hole tube 3 communicate with each other via headers 6 and 7 to form an in-tube circuit through which a heat medium flows.

[0024] FIGS. 4 (a), 4 (b) and 4 (c) show the state of the flat multi-hole tube 3 after pressure expansion by a cross section. FIGS. 5 (a) and 5 (b) show how the partition wall 15 of the flat multi-hole tube 3 is extended. The compressed fluid can be supplied to the flat multi-hole tube 3 through the headers 6 and 7. The internal pressure of the parallel flow path 14 can be increased by the compressed fluid, and the flat multi-hole tube 3 can be expanded (pressurized expansion). By expanding the tube, as shown in Fig. 4 (a), the flat multi-hole tube 3 and each fin 2 are in close contact with each other. To do. In heat exchange ^^ 1, headers 6 and 7 and end 4 of flat multi-hole tube 3 are joined in advance. For this reason, as shown in FIG. 4B, the bent partition 15 is not extended at the end 4. In other parts including the part penetrating the fin 2, the bent partition wall 15 is extended as shown in FIG. 4 (c).

[0025] The partition wall 15 of the flat multi-hole tube 3 used for heat exchange has a thickness ti, and one of the two sides forming the chevron has a length a. The distance between the partition walls 15 between the inner surfaces of the outer wall 21w of the outer tube 21 is the distance Li. Further, the thickness to of the outer tube 21 satisfies the condition of the following formula (1).

[0026] [Equation 1]

Li.t a-ti one… hi)

3a

[0027] Consider expanding the flat multi-hole tube 3 including the partition wall 15 having a cross-sectional shape in which two sides 27 having a length a on one side are bent in a mountain shape at an angle 2Θ. As shown in Fig. 5 (a), when the internal pressure is increased, due to the force acting on the wall 21w of the outer pipe 21, the partition wall 15 bent in a mountain shape is pulled up and down, and the inclination angle Θ of one side 27 is Deforms to approach 90 degrees. This deformation is called deformation in which the inclination of the partition wall changes or angular deformation. In this angular deformation, the corner (root) 26 where the partition 15 is connected to the wall 2 lw of the outer tube 21 and the apex 25 where the two sides 27 forming the chevron intersect are approximately the thickness ti of the partition 15. It is assumed that it will end in an offset state and will end. This state is shown in FIG.

[0028] The subsequent deformation is assumed to be a deformation (tensile deformation) due to tension in which the wall thickness of the partition 15 decreases, as shown in FIG. 5 (b). Therefore, the deformation mechanism of the partition wall 15 changes depending on the applied internal pressure. For this reason, it is considered that the partition wall 15 can be stably deformed until it is almost stretched by adjusting the pressure in the range from the end of the angular deformation to the start of the tensile deformation. It is done.

[0029] FIG. 7 shows the results of actual measurement of the relationship between the inner height (inner diameter or inner dimension in the minor axis direction Y) Hi and the inner pressure (pressurizing pressure) of the tube. The solid line A1 shown in FIG. 7 is a measurement value when the plate thickness ti of the partition wall 15 is 0.19 mm, and the alternate long and short dash line A2 is a measured value force of the bent angle Θ of the partition wall 15 as tangent It is a calculated value. As can be seen from the solid line A1, the bulkhead 15 When the thickness ti is 0.19 mm, the tube height Hi suddenly increases and the partition wall 15 is angularly deformed when the internal pressure exceeds approximately 2 MPa. When the internal pressure is around 7.2 MPa, the deformation amount of the partition wall 15 starts to decrease, and when the internal pressure is about 7.5 MPa, the deformation of the partition wall 15 is almost eliminated. 7. When the pressure of about 5 MPa is applied, the partition wall 15 is in a stretched state. Even if a higher pressure is applied, the deformation of the partition wall 15 does not progress, and the angular deformation of the partition wall 15 is completed. Conceivable.

[0030] In FIG. 7, when the calculated value indicated by the one-dot chain line A2 and the measured value indicated by the solid line A1 are compared, as shown in the figure, at the point of rtan Q = HiZ (2ti), The angular deformation of the tube is almost complete. Thus, as described above, when the apex 25 of the partition wall 15 is shifted from the root portion 26 by the thickness ti of the partition wall 15, the partition wall 15 is stretched and angular deformation occurs. It is guessed that it has ended. Judging from the measured value A1, the angular deformation ends when the internal pressure is about 7-8 MPa. Therefore, if the pressure when expanding the tube is about 7 to 8 MPa, if the pressure can be set higher than that, the partition wall 15 can be stretched.

As shown in FIG. 8, there is a tolerance in the thickness ti of the partition wall 15. Due to the tolerance, the relationship of deformation (tube height) Hi to the internal pressure P changes. If the target value of height Hi when expanding the tube is set to a position where angular deformation has not been completed, such as H2 in the figure, the internal pressure P is set by individual tubes so that the height Hi becomes the target value H2. It must be controlled. Such pipe expansion work is not economical, and the dimensional accuracy after pipe expansion decreases, so the heat exchange yield using flat multi-hole pipes also decreases. On the other hand, if the target value for the height Hi when expanding the tube is set to the position where the angular deformation has been completed, such as H3 in the figure, the internal pressure during the expansion will be changed as indicated by P3 in the figure. It can be set to the value of the pressure to end or higher. Therefore, regardless of the tolerance of individual tubes, it can be expanded at the same height H by expanding at the same pressure. Accordingly, since the dimensional accuracy of the tube 3 after the tube expansion is stabilized, the yield and quality of the heat exchanger 1 employing the flat multi-hole tube 3 is improved.

[0032] Thus, in the flat multi-hole tube 3, by expanding the tube 15 until the partition wall 15 is stretched, that is, until the target value H3 shown in FIG. 8 is reached, stable tube expansion is possible. Like that The pressure P3 shown in Fig. 8 is the pressure required to perform proper pipe expansion. At this pressure P3, the thickness to of the outer wall portion 21w of the outer pipe 21 is determined so that almost no deformation is seen on the outer surface of the pipe. To do.

[0033] The force (internal pressure) required for the angular deformation of the partition wall 15 can be calculated from the force applied when the partition wall 15 shown in FIG. 6 is extended. One condition is that at least the outer wall 21w of the outer tube 21 is not significantly deformed when the internal pressure is applied. In FIG. 6, the length of one side 27 of the partition wall 15 is a, the inclination (tilt angle) is 0, the distance between the surfaces of the partition wall 15 on the inner surface of the outer wall portion 21w of the outer tube 21 (the surface facing the partition wall 15) The outer wall when the internal pressure P is applied, where Li is the distance between the two surfaces and Li is the height of the flat multi-hole tube (tube) 3 (the inner diameter or inner dimension of the outer tube 21 in the short axis direction X). The stress σ ο generated in the part 21w is as follows. First, since the outer wall 21w can be regarded as a fixed beam at both ends that receives an evenly distributed load of pressure に at the partition wall distance Li, the maximum bending moment Mmax and the section modulus Z can be expressed by equations (4) and (5), respectively. It becomes. Therefore, the maximum stress σ ο applied to the outer wall 21w is given by equation (6).

[0034] [Equation 4] λ _{/ Γ} P-Li ²

Mmax = ·

[0035] [Equation 5] to

•(Five)

[0036] [Equation 6]

Mmax P-Li P-Li

σ o = = • (6)

Z 12 to 2to ² bulkhead 15 is pulled up and down by the force generated at root 26. The base 26 receives a force (load) W (W = applied pressure PX pressure receiving surface length Li) by the internal pressure P. It is considered that the bulkhead 15 is deformed by generating a bending moment at the central vertex portion 25 where the root 26 and the two sides 27 are connected. At this time, the bulkhead 15 receives the concentrated load W ′ at the center 25 and is fixed at both ends with an actual length of 2a and a height of ti. Can be modeled as a constant beam. Concentrated load applied to bulkhead 15 If force W is constant, tan Θ is the minimum when maximal, and the calculation proceeds under the condition that angular deformation is performed when concentrated load W is minimum. When tan Θ is maximized, it is a state in which the angular deformation of the partition wall 15 has been completed, and the inclination Θ can be expressed by Equation (7). Therefore, the concentrated load is obtained as shown in Equation (8).

[0038] [Equation 7]

[0039] [Equation 8]

[0040] The maximum bending moment when the partition wall 15 is angularly deformed is expressed by Equation (9). By using the section modulus Z of equation (10), the maximum stress a i generated in the partition wall 15 is as shown in equation (11). In order to model based on the cross-sectional shape of a flat multi-hole tube, the stress is obtained in one dimension.

[0041] [Equation 9]

W'-2a 2ti · P · Li '2 I if + ti ² ti · P · Li ^ i I if + ti

Mmax (9)

8Hi 2Hi

[0042] [Equation 10]

Z = —-"(10)

[0043] [Equation 11]

Mmax ti-P-Li ^ (m / 2f + ti ² 6 — 3P'Li f / 2) ² + ti σ l: fi • (11)

Z 2Hi ti Hi-ti

In order to expand the tube under the above-described conditions, the outer wall 21 is in a pressure range in which the partition wall 15 is angularly deformed. If w does not deform, it is good. Therefore, when the minimum pressure Pmin for pipe expansion is applied to the flat multi-hole pipe 3, the limit stress σ ΐίπι of the metal material including the outer wall 21 w and the partition wall 15 such as aluminum or copper is obtained. The equation (12) may be established between the maximum stress ai when the partition wall 15 is angularly deformed and the maximum stress σ ο applied to the outer wall 2 lw.

[0045] [Equation 12] σ o≥ alim σ ι · · * Γι)

[0046] The above condition (1) can be derived from the equation (12). Note that the length a of the side 27 of the partition wall 15 is expressed by the following equation (13).

[0047] [Equation 13] a = 7 (Hi / 2) ² + ti ² ---(13)

[0048] One advantage of the flat multi-hole tube is that the strength of the flat tube can be ensured by the partition wall installed inside, so that the outer wall 21w, that is, the outer tube 21, can be thinned. Here, consider a two-hole tube with two flow paths 14, which is the smallest unit of a flat multi-hole tube. As described above, the maximum stress σ o generated in the outer wall 21 w when the internal pressure P is applied is expressed by Equation (6). In the case of a flat tube with the same cross-sectional area as the two-hole tube, i.e., a flat tube with a distance of 2 Li between the partition walls and a tube inner dimension (height) of Hi, The 21w thickness to needs to be doubled. For this reason, if the thickness of the outer wall 21w exceeds twice the minimum value obtained by Equation (1), this one advantage of the flat multi-hole tube is lost. Therefore, it is desirable that the thickness to of the outer wall 21w satisfies the condition (2).

[0049] [Equation 2] two ^{Li-ti- a 2 - 1,} +ヽ

2, ≤to ... (2)

V 3a

On the other hand, in FIG. 8, when the pressure P is further increased, the partition wall 15 is pulled and deformed, and the partition wall 15 is continuously stretched while being thinned. In this case, it is not easy to determine the timing at which the partition wall 15 breaks. For this reason, it is not desirable to expand the pipe using a pressure P that initiates tensile deformation. The pressure when expanding the pipe is the upper limit of the pressure resistance of the flat multi-hole tube or Thus, the outer wall 21w of the outer tube 21 does not need to be able to withstand the pressure P at which tensile deformation starts, without deformation. Further, from the viewpoint of economy and heat exchange efficiency, it is preferable that the thickness to of the outer tube 21 is thin. Therefore, the thickness to of the outer tube 21 may be a value that deforms at a pressure at which the partition wall 15 undergoes tensile deformation. Furthermore, if the outer wall 21w is deformed when a pressure P is applied that causes the partition wall 15 to be tensilely deformed, the appearance force of the flat multi-hole tube 3 is clearly increased because the excessive pressure is applied. It can be used as one of the judgment factors for confirming the quality of the hole tube 3 and heat exchange using it.

[0051] When the partition wall 15 is subjected to tensile deformation, the tensile stress a s acting on the partition wall 15 is expressed by Equation (14).

[0052] [Equation 14] ti

[0053] It is considered that the outer wall 21w may be deformed before the partition wall 15 undergoes tensile deformation. Therefore, when the maximum pressure Pmax for pipe expansion is applied to the flat multi-hole tube 3, the limit stress σ lim of the material of the flat multi-hole tube 3, the stress σ s when the partition wall 15 undergoes tensile deformation, and the outer wall Equation (15) may hold between the maximum stress σ ο applied to 21w.

[0054] [Equation 15] σ s≥ alim σ ο ··· <Ί5)

[0055] The force of this equation (15) can also lead to the condition (3), and the thickness to of the outer wall 21w more preferably satisfies this condition.

[0056] [Equation 3]

Li'ti,,,

^ | ^ ≥to ... (3)

[0057] Fig. 9 shows the thickness to of the outer wall 21 w of the flat multi-hole tube 3 where the target value of the inner dimension Hi when expanding the tube is 1.5 mm with respect to the distance Li between the partition walls and the partition plate thickness ti. It is shown. The surface Cu shown in FIG. 9 shows the upper limit of the thickness to by the condition (3), and the surface C1 shows the lower limit of the thickness to by the condition (1). A flat multi-hole tube 3 with an outer tube 21 with a thickness to within this range is shown in Fig. 8. It is possible to set the appropriate pressure P3 for expanding the tube, and the tube can be expanded with a high yield. In addition, deformation of the outer wall 21w can be prevented when the pipe is expanded, and the heat exchange 1 with high heat exchange efficiency, which has a sufficient contact area with the fin 2 by the flat multi-hole pipe 3 with a stable outer shape, is obtained. Can be manufactured well. The specific value of pressure P3 suitable for expanding the inner dimension Hi until the desired target value is reached within the range of angular deformation without causing the bulkhead 15 to undergo tensile deformation is the flat multi-hole tube 3. It can be set based on the critical stress σ lim of the material to be used. Referring to Equation (12) and Equation (15), it can be seen that it is preferable to set the pressure P3 for pipe expansion within the following range.

[0058] [Equation 16]

[0059] In the above description, the process of manufacturing the heat exchanger 1 having the plate-like fins 2 has been described. The shape of the force fins is not limited to the plate shape, but may be a corrugated fin having a waveform. good. In a heat exchanger that uses corrugated fins, it is not necessary to expand the portion connected to the fins that is good just by expanding the portion attached to the header in the flat multi-hole tube. However, it is possible to increase the contact area by expanding the flat multi-hole tube after joining the fins. When the inside of a flat multi-hole pipe is divided into fine flow paths by a plurality of partition walls, the cross-sectional area of each flow path is small. A method of extending the partition wall by injecting a fluid and increasing the internal pressure is suitable. By adopting a flat multi-hole tube that satisfies the above-mentioned condition (1), the partition wall can be used regardless of whether it is a method of increasing the internal pressure (sometimes referred to as pressure expansion) or expansion by a tube. Before extending to the desired size, it is possible to prevent the outer wall of the outer tube from being deformed by the internal pressure of the fluid or the expander, and the outer wall of the outer wall from being deformed into a wavy state. That is, when a flat multi-hole tube is expanded by internal pressure, such as by pressure expansion, the bulkhead can be stretched while suppressing deformation of the outer wall of the tube, and the outer shape of the tube is increased until the flat multi-hole tube reaches a desired size. Can be controlled. By preventing the outer wall of the tube from being deformed into an unintended shape, a sufficient contact area can be secured between the outer surface of the tube and the fins, improving heat transfer performance. I can go up. Therefore, a highly reliable heat exchanger with high heat exchange efficiency can be provided.

Claims

The scope of the claims

A flat outer tube,

Having a plurality of partition walls dividing the inside of the outer tube into a plurality of flow paths;

Each partition wall has a thickness ti, has a cross-sectional shape bent into two chevrons with one side length a, and is arranged so that the distance between the partition walls on the inner surface of the outer tube is a distance Li. The thickness of the outer tube is a flat multi-hole tube satisfying the following conditions.

[Number 1]

[2] Thickness of the outer tube mentioned above ttoo will satisfy the following conditions more and more fully, and the flatness of claim 11 Flat multi-hole tube. .

[[Number 22]]

The flat multi-hole tube according to claim 1, wherein the thickness to of the outer tube further satisfies the following conditions.

[Equation 3]

A plurality of flat multi-hole tubes according to claim 1;

A heat exchanger having a plurality of fins attached in a state where the plurality of flat multi-hole tubes are penetrated.